The development of large scale image capture and image display devices such as radiographic imaging panels and liquid crystal display devices requires large scale arrays of radiation detection sensors in the first instance and similarly large scale arrays of imaging pixels in the second.
Both the radiation detection sensors and the imaging pixels comprise complex electronic structures which include electronic switching devices in addition to means to either capture an electronic charge representing incident radiation, or means to alter the state of a liquid crystal material to display a visible image.
Radiation detection panels, particularly panels intended for medical radiography applications must be at least 14".times.17" to be commercially useful. Similarly, liquid crystal displays must be of the order of at least 8".times.10" for a laptop personal computer application, and substantially larger for television displays.
Each of those panels comprises a number of individual detectors or display pixels which is in the millions. For instance a 14".times.17" diagnostic quality radiation detection panel will have approximately eight million detectors arrayed in regularly spaced lines and columns, with multiple conductors running in the interstitial spaces between detectors for accessing the detectors and retrieving the signals representing the radiogram. Each detector comprises at least one switching element, usually a Thin Film Transistor, coupled with the actual radiation detector. Even with the currently high quality manufacturing abilities available, yields of commercially useful panels with so many elements are relatively low, and as a result, the cost of such large size panels is high.
The yield rate is related to the overall number of elements in a panel, and rises with the square of the panel size. It is therefore often advantageous to assemble into larger panels of the desired size a plurality of smaller panels which may be produced at higher yields at substantially lower cost. This process of making larger panels from a plurality of smaller panels is typically referred to in the art as "tiling". U.S. Pat. No. 5,381,014 issued to Jeromin et al., whose contents are incorporated herein by reference, as well as U.S. Pat. No. 5,254,480 issued to Tran, and U.S. Pat. No. 5,315,101 issued to Hughes et al., describe such tiling process.
The process for assembling the smaller panels or submodules, into a larger panel, typically involves adjoining two or four submodules by placing an adhesive along the adjoining edges and adhering the submodules to each other. The aforementioned Jeromin et al patent teaches placing the submodules to be joined on a supporting dielectric base and adhering the submodules both to each other and to the supporting base. Still according to the teachings of Jeromin et al., the abutting submodule edges are ground to a high degree of precision and contain a beveled portion in the vicinity of the supporting base.
Typically, after joining the submodules, completion of an imaging panel entails depositing a continuous radiation detecting material layer such as selenium, or a continuous image display layer, over the assembled submodules to provide a means to detect incident radiation or to display an image.
While this technique has provided generally good results, it has been observed that the larger panel response to in the vicinity of the submodule juncture is deficient. The deficiency has been tracked, among other reasons, to the formation of bubbles in the imaging layer above the junction between the panels. We will refer to this junction hereinafter as the "seam". These bubbles were attributed to gas being released from the adhesive in the seam, typically an epoxy, during deposition of the imaging layer.
There is need therefore, to provide a method of alleviating this gassing problem in the seams between adjacent submodules.